Bank Deposits Are Better Than Engine Deposits

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The history of the automobile is a history of innovation. It is also a history of unintended consequences. That is, efforts to solve one problem have often created other problems. For example, the reduction of ZDDP content in motor oils resulted in premature wear for flat-tappet cams in older cars. The push in recent years toward smaller, fuel-efficient yet powerful engines and the associated key technologies used to achieve that combination has its own set of new byproducts: engine deposits of a different caliber in places that never used to see them.

Deposits come in many different forms and are often the result of unburned or partially burned fuel, metal fragments from component wear, oil that has broken down or dirt/debris that finds its way into the engine. The most common causes of deposit formation are excessive idling and short trips, which prevents the oil from cycling through the crankcase; dirt and debris; moisture/fuel contamination; lack of maintenance; and hot spots, which can bake clumps and oil right onto parts of the engine.

Excessive deposits contribute to hard starts, misfiring, a trouble light going on because of a bad oxygen sensor, engine overheating or increased oil consumption. Ultimately, deposit formation leads to inefficient engine operation that produces lower fuel mileage, lost power, knocking, pinging and increased emissions.

Two of the culprits today are gasoline direct injection (GDI) and turbochargers. Both are being heralded for certain advantages in fuel consumption as compared to conventional fuel injection and traditional induction setups. GDI also produces more power than a conventional engine with identical displacement. What GDI amounts to, is that the fuel is being injected directly into the combustion chamber of each cylinder and not into the intake tract. That is, the injectors are right there in the cylinder itself.

GDI and turbochargers are now common features of passenger cars and light trucks. By 2020, industry experts predict nearly every new vehicle will feature GDI technology, and the vast majority will be turbocharged. While these advanced technologies enhance performance, they also present serious challenges for motor oil.

Turbochargers push more air into the engine’s combustion chamber, providing better fuel economy and performance, but also creating intense engine temperatures. They often operate above 150,000 rpm on exhaust gases exceeding 1000 degrees Fahrenheit. These extreme conditions cause some motor oils to break down and solidify into harmful deposits.

Vehicle manufacturers have long recommended a different service interval based on normal and severe driving conditions. Turbocharged vehicles are automatically included in the severe service category due to the extreme heat they generate. Motor oil with unique properties is required to combat the effects of intense temperatures.

One of the problems with contemporary engines is that oil vapor inside the engine is getting into places where it gets baked on and is difficult to clean. Two of these places mechanics have had to deal with are on the backsides of valves and on intake throttle bodies.  

Motor Oil and the New Technologies

The VVT Issue: Variable valve timing (VVT) uses motor oil as a hydraulic fluid to move the necessary components to ensure the cam phasers provide extra rotation to the camshaft which adjusts when the valves open and close to increase efficiency. Typically, VVT components contain tiny openings through which the oil must flow, acting as hydraulic oil to function properly. Even the slightest amount of deposits can lodge in these tiny openings and negatively affect the system.

Reducing the negative impact of deposits requires a combination of proper maintenance, high-quality motor oil and filtration. Premium synthetic oils resist deposits and sludge better than conventional oils, helping keep sensitive VVT components clean and functioning properly. Premium synthetic oils also resist viscosity loss, meaning they consistently perform the duties of a hydraulic fluid, which is vital to proper operation of VVT components.

The Turbocharger Issue: Turbos’ center section contains an oil-lubricated bearing. The tremendous heat and stress turbos create can cause some oils to break down and form harmful bearing deposits, known as turbo coking. Over time, turbos can suffer reduced performance or fail altogether.

This is one reason the bar keeps being raised for motor oil performance requirements. It’s also one of the reasons organizations like the Petroleum Quality Institute of America are paying attention to what is being sold out there. An example of the scrutiny of oils’ ability to prevent deposits is the thermo-oxidation engine oil simulation test 33C test (ASTM D6335), an industry-standard bench test that simulates turbocharger operating conditions. To meet the API SN Resource Conserving and ILSAC, GF-5 motor oil specifications that are often recommended by vehicle manufacturers, a 5W-30 motor oil must limit total deposit formation to 30 milligrams or less. Synthetic oils typically report much better performance in this challenging deposit test.

Closing Thought

Diagnosis is the first step toward solving a health problem, and the same goes for problems in cars. Manufacturers and top mechanics are aware of the problems these new technologies are now bringing, hence the need for better oil performance. Premium synthetic oils are the solution, and that’s advice you can bank on.  


ED NEWMAN is the advertising manager for AMSOIL INC., an independent manufacturer of synthetic lubricants. He’s been writing articles about synthetic oil since 1986. He can be contacted at For more information, visit:

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